24. THE ORCHIDS OF NEIW ENGLAND. 
that cross-fertilization is thoroughly insured, though Orchids 
offer sap only to their visitors.” 
“Species with a short and not very narrow nectary,”’ says 
Darwin, “are fertilized by bees and flies; those with a much 
elongated nectary, or one having a very narrow entrance, by 
butterflies and moths.” “The concealment of the honey in a 
nectary, protected by other parts of the flower,” says Muller, 
‘protects the honey from rain, and permits a larger supply to 
be accumulated, thus attracting visitors in an increased degree.” 
With these disadvantages: “The honey is the less easily dis- 
covered the more it is protected, so that a great host of the 
less acute visitors are excluded; and the more intelligent 
visitors which are able to detect it, cannot obtain it so quickly 
as if it were more exposed, so that the work of fertilization 
goes on more slowly.” But “exclusion of the multitude of 
less intelligent short-lipped visitors is only injurious so long as 
more specialized visitors are not abundant enough to accom- 
plish all the work of fertilization,” and “delay in this work, 
owing to concealment of the honey, is diminished by a great 
variety of contrivances, and sometimes entirely removed, .. . 
pathfinders (colored spots or lines) point towards the honey, 
and enable the more intelligent visitors to find it in a moment; 
delay in obtaining deeply-placed honey is lessened by the 
development of convenient standing-places, of apertures spe- 
cially fitted for the insect’s head or proboscis,” etc. He 
supposes that “the first honey-yielding flowers exposed their 
honey on flat surfaces, and that the first flower-visiting insects 
were only furnished with organs capable of licking up freely 
exposed honey. Under these circumstances, elongation of the 
proboscis would be of no advantage to any insect, but shelter 
from rain and increased room for accumulating honey would 
be beneficial to the plant, even before insects became divided 
into short-tongued and long-tongued.” With these changes in 
the structure of the plant, it came to pass that only those 
